The present invention relates to a method of dry etching and particularly to a method of low-temperature dry etching suitable for formation of various patterns having a tapered sidewall.
As is well known, with an increase in the density of integration of a semiconductor device and a decrease in the size of various elements, such as a resistor or a transistor, a recent trend in a wiring, an insulating film, etc. is to have a perpendicular sidewall for the purpose of decreasing the necessary area. However, this expedient has raised a problem that when another wiring or insulating film is formed on the perpendicular wiring or insulating film, a newly formed wiring or insulating film comes to be cut by the sharp edge of the underlying wiring or insulating film. In order to overcome this problem, the sidewall of the wiring, insulating film, or the like has been tapered in such an extent that the above-described cutting can be prevented. Therefore, there has been desired a method of dry etching which enables an article, such as a wiring or an insulating film, to be etched while regulating the taper of the sidewall of the article with high accuracy (in the present specification, the above-described dry etching for forming a pattern having a tapered sidewall is hereinafter referred to as "taper dry etching").
A conventional method of taper dry etching proposed in, for example, Proceeding of Dry Process Symposium, (IEE of JAPAN, Tokyo) P48 (1984) comprises etching an article to be etched by introducing a mixture composed of an etching gas and a depositing type gas into a reaction chamber.
However, this method has a problem that the incorporation of a depositing type gas brings about lowering in both the etching rate and the selection ratio. Further, since the depositing type gas is deposited on a semiconductor substrate to be etched, the deposition brings about the contamination of the surface of the substrate. This in turn causes a lowering in the yield of the product.